1. Field
The present invention relates to a rotational atherectomy system for removing a stenotic lesion from within a vessel of a patient. More specifically, the invention relates to a rotational atherectomy system with enhanced distal protection capability for removing or reducing stenotic lesion in a human artery by rotating an abrasive element within the artery to partially or completely ablate the stenotic lesion and simultaneously remove out of the patient's body abraded particles (embolic particles or debris) released into the treated artery during the rotational athererctomy procedure. It should be understood that rotational atherectomy devices and rotational athererctomy procedures are often referred to as rotational angioplasty devices and rotational angioplasty procedures. One type of rotational atherectomy devices is referred to as an orbital atherectomy device. All these terms may be used interchangeably herein.
2. Description of the Related Art
Atherosclerosis, the clogging of arteries, is a leading cause of coronary heart disease. Blood flow through the peripheral arteries (e.g., carotid, femoral, renal, etc.), is similarly affected by the development of atherosclerotic blockages. One conventional method of removing or reducing blockages in blood vessels is known as rotational atherectomy. A device and a method for performing the Rotational Atherectomy Procedure are known from U.S. Pat. No. 4,990,134 to Auth. A rotational atherectomy (angioplasty) device based on this patent is commercially available from Boston Scientific Corporation of Natik, Mass., USA.
The distal end portion of this prior art device is shown in FIG. 1. The abrasive burr 1 of this Auth device is attached to a distal end of a hollow flexible drive shaft 2. The abrasive surface of the burr is formed from diamond particles 3. The device is rotated around a special guidewire 4, which is advanced across the stenotic lesion. The device is advanced towards the stenotic lesion around (over) the guidewire. The abrasive burr is positioned against the occlusion and the drive shaft is rotated around the guidewire at extremely high speeds (e.g., 20,000-160,000 rpm). As the abrasive burr rotates, the physician repeatedly advances it towards the stenotic lesion so that the abrasive surface of the burr scrapes against the occluding tissue and disintegrates it, reducing the occlusion and improving the blood flow through the vessel. It should be understood that the terms abrasive burr and abrasive element may be used interchangeably herein.
U.S. Pat. No. 6,132,444 to Shturman (the instant inventor) et al., describes a rotational atherectomy device comprising an abrasive element 11 which is located proximal to and spaced away from a distal end of the drive shaft 12. This abrasive element is formed from diamond particles 13 directly electroplated to wire turns 14 of an enlarged diameter portion 15 of the drive shaft 12. The enlarged diameter portion 15 of the drive shaft is asymmetric and is responsible for providing an abrasive element with a centre of mass which is spaced away from the rotational axis of the drive shaft. The device is rotated around a special guidewire 4 and its eccentric abrasive element 11 is able to open the treated stenotic lesion to a diameter substantially larger than the maximum diameter of the abrasive element.
FIG. 3 shows a side sectional view of the distal end portion of a third embodiment of the rotational atherectomy device of the prior art. The device of FIG. 3 is similar to the device of FIG. 2 except that the abrasive element comprises a prefabricated abrasive crown 16 disposed around the eccentric enlarged diameter portion 15′ of the drive shaft 12′. The prefabricated abrasive crown 16 is known from U.S. patent application Ser. No. 10/272,164 to Shturman (the instant inventor). The prefabricated abrasive crown 16 is formed from the diamond particles 13′ bonded to a metallic sleeve 17 rather than directly to wire turns 14′ of the drive shaft 12′. The device is rotated around a special guidewire 4, and it is commercially produced by Cardiovascular Systems, Inc. of Minnesota, USA.
FIG. 4 illustrates in longitudinal cross-section operation of a rotational atherectomy device known from WO 2006/126176 to Shturman (the current inventor). The rotational atherectomy device (of FIG. 4) comprises a solid eccentric abrasive element and two solid asymmetric support elements 20D, 20P mounted on a hollow flexible drive shaft 21. The solid asymmetric support elements 20D, 20P have their centres of mass spaced away (offset) from a rotational (longitudinal) axis of the drive shaft 21 and, during rotation of the drive shaft, act as counterweights to the eccentric abrasive element 33. Preferably, the rotational atherectomy device includes a distal solid counterweight 20D located on the drive shaft 21 distal to and spaced away from the abrasive element 33 and, a proximal solid counterweight 20P located on the drive shaft 21 proximal to and spaced away from the abrasive element 33. In the most preferred embodiment of the invention, the centre of mass of each of the solid counterweights is separated from the centre of mass of the abrasive element by an angle of 180 degrees around the axis of the drive shaft. When the drive shaft of the rotational atherectomy device with solid counterweights is rotated, centrifugal forces generated by the solid counterweights 20D, 20P and the eccentric abrasive element 33 preferably act in substantially the same plane but in opposite directions. These centrifugal forces cause the distal end portion of the drive shaft to flex and assume a generally bowed or arcuate shape. During rotation of the drive shaft, the abrasive element and each of two solid counterweights move in orbital fashions around the axis of rotation of the drive shaft in orbits that are substantially larger than the respective diameters of the abrasive element or solid counterweights.
The method of use of the device preferably includes the step of partially withdrawing the guidewire 4′ into the lumen of the drive shaft such that the distal end of the guidewire 4′ is located within the lumen of the drive shaft 21 proximal to the distal end portion of the drive shaft. Pressure applied by the abrasive element and the solid counterweights to the tissue to be removed or to the inner surface of the vessel wall can be easily controlled by adjusting the rotational speed of the drive shaft (i.e. the faster the speed of rotation, the greater the applied pressure), as well as by selecting the respective weights of the abrasive element and solid counterweights. It should be noted that the eccentric disposition of the abrasive element and solid counterweights is not limited to their geometrical eccentric position but, much more importantly, involves the eccentric disposition of their centers of mass with respect to the rotational axis of the drive shaft.
It should be understood that the terms ‘solid counterweight’, ‘solid asymmetric support element’ and ‘solid support element with a centre of mass offset from a rotational axis of the drive shaft’ are used interchangeably throughout the specification.
FIG. 5 illustrates in longitudinal cross-section operation of a fifth embodiment of the rotational atherectomy device of the prior art. This rotational atherectomy device is known from WO 2006/126175 to Shturman (the current inventor) The rotational atherectomy device (of FIG. 5) comprises a solid abrasive element 35 and two solid support elements 22D, 22P mounted on a hollow flexible drive shaft 21′. The device of FIG. 5 is similar to the device of FIG. 4 except that the solid abrasive element 35 and the solid support elements 22D, 22P are symmetric with respect to a rotational (longitudinal) axis of the drive shaft 21′ (i.e. they have their centres of mass lying on (the) a rotational (longitudinal) axis of the drive shaft 21′. FIG. 5 illustrates operation of the device in a curved vessel. The device is rotated around a special guidewire 4′ which has to be withdrawn into the drive shaft 21′ prior to starting its rotation.
In all of the prior art rotational atherectomy devices such as described above with reference to FIGS. 1 to 5, an elongated drive shaft is rotatable around a stationary guidewire. A long proximal portion of the drive shaft is rotatable within an elongated stationary drive shaft sheath 24, said drive shaft sheath 24 forming an annular lumen between the stationary sheath and the rotatable drive shaft. A saline solution or special lubricating fluid is pumped into the annular lumen between the stationary sheath and the rotatable drive shaft. A portion of said saline solution or special lubricating fluid is able to pass between adjacent wire turns of the drive shaft into a second annular lumen formed between the drive shaft and the guidewire thereby reducing friction between the drive shaft and the guidewire. In all of the prior art rotational atherectomy devices referred to above the antegrade flowing saline solution ‘FF’ or special lubricating fluid enters the treated vessel from a (the) distal end of the stationary drive shaft sheath 24 and thereby entrains and propels distally in an antegrade direction ‘FF’ along the treated vessel 100 embolic particles (debris) abraded by the abrasive element. The distal migration of the embolic particles along the treated vessel and potential embolisation of very small diameter arteries or capillaries by the embolic particles is of major concern to physicians who practice in this field. Potentially life-threatening complications which may be caused by the embolic particles produced during the rotational atherectomy procedure prevent use of the above described rotational atherectomy devices for treatment of stenotic lesions in the carotid arteries.
Currently, several types of filter based distal embolic protection devices (EPDs) are commercially available for use during balloon angioplasty procedures. These devices are designed to prevent migration of embolic particles larger than 100 microns and cannot prevent migration of very small embolic particles produced during rotational atherectomy procedure. One concept of providing a rotational atherectomy device with distal embolic protection capability is known from U.S. Pat. No. 5,681,336 (to Clement et al.). According to this concept, migration of abraded embolic particles along the treated artery is prevented by temporarily occluding the treated artery distal to the stenotic lesion and aspirating abraded particles from the treated artery prior to deflating a guidewire mounted occlusion balloon. The rotational atherectomy device known from U.S. Pat. No. 5,681,336 (to Clement et al.) has a complicated construction and is difficult to manufacture on a commercial scale.
Disadvantages associated with either limited or completely absent distal embolic protection of all commercially available rotational atherectomy devices have been addressed in WO 2006/126076 to Shturman (the instant inventor). In accordance with WO 2006/126076 every rotational atherectomy device of the prior art described below and shown in FIGS. 6 to 16C differs from the devices of the prior art described above and shown in FIGS. 1 to 5 in that its drive shaft has a fluid impermeable wall and allows an antegrade flow FF of pressurised fluid through a lumen of the drive shaft from a proximal end towards a distal end of the drive shaft. A portion of the pressurised fluid, after entering the treated vessel distal to the abrasive element, flows in a retrograde direction ‘RF’ around the abrasive element and across the treated stenotic lesion to entrain abraded embolic particles ‘EP’ and evacuate them from the treated vessel as soon as they have been abraded by the abrasive element of the device. Several embodiments of the device with distal embolic protection capability are disclosed in WO 2006/126076, but in every one of these embodiments the retrograde flowing fluid RF and entrained embolic particles EP are evacuated through an oval lumen formed between a stationary drive shaft sheaf and the rotatable fluid impermeable drive shaft. The retrograde flowing fluid RF and entrained embolic particles EP are evacuated from the patient's body.
FIG. 6 is a side sectional view of the distal end portion of a sixth embodiment of the rotational atherectomy device of the prior art. The device of FIG. 6 is similar to the device of FIG. 4 except that the hollow drive shaft 42 has a fluid impermeable wall. The hollow drive shaft 42 is formed from a torque transmitting coil 43 and a fluid impermeable membrane 47. FIG. 6 shows that the membrane 47 lines an inner surface of the torque transmitting coil 43. FIG. 6 illustrates that this device is provided with distal protection capability, i.e. embolic particles abraded by the abrasive element 33′ are evacuated from the treated vessel 100. This device represents one of the embodiments of the rotational atherectomy device described in WO 2006/126076. FIG. 6 shows that pressurised flushing fluid flows in an antegrade direction FF along the lumen of the drive shaft 42 and enters the treated vessel 100 through a luminal opening located distally to the abrasive element. A portion of this fluid flows in a retrograde direction RF around the abrasive element 33′ and across the stenotic lesion 105 to entrain embolic particles EP abraded by the abrasive element. These embolic particles are aspirated into an annular lumen formed between the rotatable drive shaft 33′ and its stationary sheath 24′ and removed from the patient's body. FIG. 6 illustrates the device with a solid eccentric abrasive element 33′ and a pair of solid support elements 20D′, 20P′ which have their centres of mass spaced away (offset) from the rotational (longitudinal) axis of the drive shaft. During rotation of the drive shaft, these solid support elements act as counterweights to the eccentric abrasive element The device of FIG. 6 may be advanced across the stenotic lesion over a conventional guidewire, but the guidewire has to be removed from the device prior to attaching a detachable fluid supply tube to the device.
FIG. 7 is a side sectional view of the distal end portion of a seventh embodiment of the rotational atherectomy device of the prior art. The device of FIG. 7 is similar to the device of FIG. 6 except that the solid abrasive element 35′ and the solid support elements 22D′, 22P′ are symmetric with respect to a rotational (longitudinal) axis of the drive shaft 42′ (i.e. they have their centres of mass lying on a rotational (longitudinal) axis of the drive shaft 42′. The hollow drive shaft of FIG. 7 is similar to the hollow drive shaft of FIG. 6 except that a fluid impermeable membrane 47′ in FIG. 7 is shown extending around a torque transmitting coil 43′ of the drive shaft 43′. FIG. 7 illustrates operation of the device in a curved vessel 100. The device of FIG. 7 has been described in WO 2006/126076 and, as any other device described in WO 2006/126076, it may be (advanced across the stenotic lesion around (over)) (used with) a conventional guidewire. The guidewire has to be removed from the device prior to attaching a detachable fluid supply tube to the device.
FIG. 8 is a side sectional view of the distal end portion of an eighth embodiment of the rotational atherectomy device of the prior art. The device of FIG. 8 is similar to the device of FIG. 6 except that the support elements 222D, 222P are fluid inflatable. These support elements 222D, 222P are in fluid communication with the lumen of the drive shaft 242 and are inflated by pressurised fluid flowing along the lumen of the drive shaft in an antegrade direction FF. Pressurised fluid inflates the support elements 222D, 222P and enters the vessel through outflow openings 225 in the distal support element. FIG. 8 shows that the support elements, when inflated, are asymmetric with respect to a rotational (longitudinal) axis of the drive shaft (i.e. the inflated support elements have there's centres of mass spaced away (offset) from the rotational (longitudinal) axis of the drive shaft). During rotation of the drive shaft, these inflated support elements 222D, 222P act as counterweights to the eccentric abrasive element 235. The device of FIG. 8 has been described in WO 2006/126076 and, as any other device described in WO 2006/126076, it may be (advanced across the stenotic lesion over a conventional guidewire. The guidewire has to be removed from the device prior to connecting (attaching) a detachable fluid supply tube to the device.
FIG. 9 is a side sectional view of the distal end portion of a ninth embodiment of the rotational atherectomy device of the prior art. The device of FIG. 9 is similar to the device of FIG. 8 except that the abrasive element 235′ and the fluid inflatable support elements 222D′, 222P′ shown in FIG. 9 are symmetric with respect to a rotational (longitudinal) axis of the drive shaft (i.e. they all have their centres of mass lying on a rotational (longitudinal) axis of the drive shaft. FIG. 9 shows operation of the device in a curved vessel 100. A stenotic lesion 105 is shown located on an inner curvature of the vessel 100. FIG. 9 illustrates a bias provided to the symmetric abrasive element 235′ by a magnetic force or forces. The magnetic force or forces are indicated by arrows marked “MF”. The device of FIG. 9 has been described in WO 2006/126076 and, as any other device described in WO 2006/126076, it may be advanced across the stenotic lesion over a conventional guidewire. The guidewire has to be removed from the device prior to connecting a detachable fluid supply tube to the device.
FIG. 9 shows an embodiment in which the centres of mass of the fluid inflatable support elements and the abrasive element are all lying on the longitudinal axis of the drive shaft. However, it is also envisaged to provide an embodiment in which the centre of mass of the abrasive element is spaced radially away from the longitudinal axis of the drive shaft while the centers of mass of both of the distal and proximal fluid inflatable support elements are lying on the longitudinal axis of the drive shaft. Such embodiment may be particularly applicable for use in carotid or femoral arteries.
FIG. 10 is a side sectional view of the distal end portion of a tenth embodiment of the rotational atherectomy device of the prior art. The device of FIG. 10 has been described in to Shturman (the instant inventor). The device of FIG. 10 is similar to the device of FIG. 6 except that the solid counterweights 200D, 200P comprise outflow channels 202D, 202P which extend radially outward with respect to a rotational (longitudinal) axis of the drive shaft 252. FIG. 10 illustrates that pressurised fluid flowing through these outflow channels 202D, 202P forms fluid bearings between the solid counterweights 200D, 200P and the wall of the treated vessel 100. This rotational atherectomy device may be advanced across the stenotic lesion over a conventional guidewire, but the guidewire has to be removed from the device prior to connecting a detachable fluid supply tube to the device.
FIG. 11 is a side sectional view of the distal end portion of an eleventh embodiment of the rotational atherectomy device of the prior art. The device of FIG. 10 has been described in to Shturman (the instant inventor). The device of FIG. 11 is similar to the device of FIG. 10 except that the outflow channels 202SD, 202SP are formed not in the solid counterweights but in the solid support elements 200SD, 200SP which are symmetric with respect to a rotational (longitudinal) axis of the drive shaft. FIG. 11 illustrates operation of the device in a curved vessel.
FIG. 11 shows an embodiment in which the centers of mass of the solid support elements 200SD, 200SP and the abrasive element 333 are lying on the longitudinal axis of the drive shaft 252′. However, it is also envisaged to provide an embodiment in which the centre of mass of the abrasive element is spaced radially away from the longitudinal axis of the drive shaft while the centers of mass of both of the distal and proximal solid support elements are lying on the longitudinal axis of the drive shaft. Such embodiment may be particularly applicable for use in carotid or femoral arteries.
FIG. 12 is a side sectional view of the distal end portion of a twelfth embodiment of the rotational atherectomy device of the prior art. The device of FIG. 12 is similar to the device of FIG. 8 except that the fluid inflatable counterweights 232D, 232P comprise outflow openings 226 located such that pressurised fluid flowing through these openings 226 forms fluid bearings between the fluid inflatable counterweights and the wall of the treated vessel 100.
FIG. 13 is a side sectional view of the distal end portion of a thirteenth embodiment of the rotational atherectomy device of the prior art. The device of FIG. 13 has been described in to Shturman (the instant inventor). The device of FIG. 13 is similar to the device of FIG. 12 except that outflow openings are formed not in the fluid inflatable counterweights but in the fluid inflatable support elements 232SD, 232SP which, when inflated, are symmetric with respect to a rotational (longitudinal) axis of the drive shaft. The outflow openings 226′ are located around entire circumferences of the symmetric fluid inflatable support elements such that pressurised fluid flowing through these openings forms fluid bearings between the walls of the fluid inflatable support elements and the wall of the treated vessel 100. FIG. 13 shows an embodiment in which the centers of mass of the fluid inflatable support elements and the abrasive element are lying on the longitudinal axis of the drive shaft. However, it is also envisaged to provide an embodiment in which the centre of mass of the abrasive element is spaced radially away from the longitudinal axis of the drive shaft while the centres of mass of both of the distal and proximal fluid inflatable support elements are lying on the longitudinal axis of the drive shaft. Such embodiment may be particularly applicable for use in carotid or femoral arteries.
FIGS. 13 to 15b (FIG. 13 to FIG. 15b) are side sectional views of the distal end portions of two modifications of a fourteenth embodiment of the rotational atherectomy device of the prior art. FIGS. 13 to 15b illustrate that the torque transmitting coil 400 does not extend to the distal end of the drive shaft 282, and the torque is transmitted to the abrasive element 450 by the fluid impermeable membrane 292 alone. FIGS. 14A and 14B show fluid inflatable support elements 432SD, 432SP which, when inflated, are symmetric with respect to a rotational (longitudinal) axis of the drive shaft 282. FIGS. 15A and 15B show fluid inflatable counterweights 432D, 432P which, when inflated, have their centres of mass offset from the rotational longitudinal axis of the drive shaft 282. FIGS. 15A and 15B illustrate a flexible leaf valve 400 which is formed at the distal end of the drive shaft 282 integrally with a wall of the distal fluid inflatable counterweight 432D. Preferably, the flexible valve 400 is moved to its closed position by pressure of fluid, which is pumped in an antegrade direction FF along the lumen of the drive shaft 282 after advancing the drive shaft over a guidewire 4 across a stenotic lesion to be treated and withdrawing the guidewire from the device. FIGS. 14A and 14B illustrate a flexible leaf valve 440 formed at the distal end of the drive shaft 282 integrally with a wall of the distal fluid inflatable support element 432SD. The distal fluid inflatable support element 432SD, when inflated, is symmetric with respect to a rotational (longitudinal) axis of the drive shaft 282.
It should be noted that FIGS. 14A and 14B show an eccentric abrasive element 450 mounted to the drive shaft between symmetric support elements 432SD, 432SP, while FIGS. 15A and 15B show counterweights 432D, 432P located on both sides of the eccentric abrasive element 460.
FIGS. 16 to 16c (FIG. 16 to FIG. 16c) are side sectional views of the distal end portion of a fifteenth embodiment of the rotational atherectomy device of the prior art. FIGS. 16 to 16c illustrate that the outer torque transmitting coil 470 does not extend to the distal end of the drive shaft, and the torque is transmitted to the abrasive element by the inner torque transmitting coil 480 alone. FIGS. 16 to 16c illustrate formation of a ball valve at the distal end of the drive shaft 282 by a ball 495 and a shoulder 497 at the distal end of the drive shaft.
All Shturman atherectomy devices known from WO 2006/126076 comprise drainage lumen which is integral to the device. Most frequently the drainage lumen has annular shape and (extends) (is formed) between the rotatable drive shaft of the device and its stationary drive shaft sheaf. It should be noted that such annular drainage lumen has limited width and will not permit removal out of the patient's body of embolic particles measuring more than 200 microns in more than one dimension. The drainage lumen need not necessarily have an annular shape but the relatively limited cross sectional dimensions of any drainage lumen formed integrally with an atherectomy device create limitations for aspirating into such drainage lumen and removal out of the patient's body of embolic particles which measure more than 200 microns in more than one dimension.